In the three years since then, Microsoft has fixed 87 vulnerabilities in various flavours of IE while Mozilla has patched 199 vulnerabilities in Firefox products.

The report, compiled by Jeff Jones, a security strategy director in Microsoft's Trustworthy Computing group, also found IE scored fewer vulnerabilities than Firefox across all categories of severity.

Mozilla said Microsoft's comparison is, at best, meaningless.

"Just because dentists fix more teeth in America doesn't mean our teeth are worse than in Africa," Mike Shaver, chief evangelist for Mozilla told eWEEK. Shaver took particular exception at Microsoft's decision to equate a large number of bug fixes with insecure software.

"It's something you'd expect from maybe an undergrad," he said. "It's very disappointing to see somebody in a senior security position come out and say that because an organisation is more transparent about their bugs and fixing them, they're somehow less secure."

Shaver added that even taken on its own merits the comparison between IE and Firefox is potentially misleading because Redmond often bundles multiple fixes in a single update, a phenomenon repeated to an even greater extent with the release of service packs.

Mozilla is putting an effort into encouraging users to update to the latest version of its software more quickly alongside greater emphasis on rapidly responding to security problems. Microsoft's efforts to suggest this is a bad thing are out of tune with the rest of the industry, Shaver argues.

"Shouldn't they be trying to fix more bugs, rather than writing reports that would 'punish' them for actively improving the security of their users rather than hoping that defects aren't found by someone who they can't keep quiet?"

"Microsoft should be embarrassed to be associated with this sort of ridiculous 'analysis'. We don't pretend that hiding the rate of fixes improves our users' security in any way, and we never will. We're transparent and aggressive in dealing with security issues, and 130 million Firefox users are safer for it every day," Shaver writes in a blog posting here.

Microsoft's Jones is no stranger to controversy. His previous study - a comparison between the number of security vulnerabilities in Windows Vista, Mac OS X, and Ubuntu Linux in the first six months of availability of the respective OSes - united Mac and Linux fans in opposition to Redmond's contention that Vista was more secure than its rivals. ®